10-year evaluation: Suzuki DF2.5 portable outboard motor

By: Andrew Norton

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  • Trade-A-Boat

The tiny Suzuki DF2.5 portable outboard motor is simply brilliant for small yacht tenders.

10-year evaluation: Suzuki DF2.5 portable outboard motor
The Suzuki DF2.5 portable outboard motor is a frugal marine engine. It provided way better long-term value than its long-deceased two-stroke counterparts.

When Suzuki Marine released its portable DF2.5 outboard motor a decade ago it didn’t stuff around. It used a tiny OHV four-stroke power head with thermostatically controlled water cooling and pressure lubrication to handle a wide range of oil viscosities for all climates. Suzuki even fitted a carry handle aft of the power head so the outboard engine could be carried one-handed over long distances. And the good prop selection ensured this small marine engine could be used on a wide range of hulls. Yet for all its innovations, such as twist-grip throttle control and a clutch, it weighed only 2.0kg more than the long-running two-stroke 55cc Suzuki DT2.2 outboard motor.

In March 2006 Haines Suzuki supplied me with a new 2.5hp Suzuki DF2.5 for long-term evaluation. The engine was so good it became part of my collection of portable small outboards and 10 years on it has never missed a beat, even if its high vibration levels on some hulls did give my ever-increasing flab a good workout.

 

Portable Suzuki DF2.5 outboard motor

Like the Suzuki DT2.2, the Suzuki DF2.5 is designed strictly for 15-inch transoms. The distance from transom bracket to anti-ventilation plate is only 16 inches, so forget using this engine on older hulls with 16-inch transoms designed for the universal short-shaft measurement of 17 inches from brackets to plate.

In designing the engine Suzuki omitted a few items I regard as essential for user-friendliness – there’s no low-oil warning light, so unknown oil starvation could cause the Suzuki DF2.5 portable engine to seize. And as there’s no pilot water discharge a look over the transom is the only way of telling if the water pump’s impeller is doing its job. Accessing the power head isn’t that easy as the recoil starter cord passes through the upper cowl, preventing it from being completely separated from the engine pan/lower cowl.

But apart from these issues the Suzuki DF2.5 outboard motor is a pretty logical design. The chromed rocker cover is a nice touch and it’s easily removed for valve clearance adjustments, and the thermostat can be quickly replaced should it fail. Four trim positions and a full tilt stopper knob are provided, along with 360° turning for full boat control.

Because the CD ignition has fixed timing only standard 91 RON unleaded should be used – the engine may suffer pre-ignition from higher octane fuel such as premium unleaded. This can be a pain as it’s getting harder to buy standard unleaded that doesn’t have some ethanol (aka weedkiller) in it. Gravity feeds fuel from the one-litre integral tank to the carbie mounted alongside the power head to reduce vapour lock on hot days.

The large capacity sump (for such a small engine) holds 0.38 litres to absorb oil dilution that occurs during extended low speed operation, such as trolling. After the first 20 hours or three months I recommend changing the oil every 50 hours or six months as no replaceable oil filter is fitted.

 

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On the water

From the time testing commenced it was obvious the Suzuki DF2.5 had nowhere near the torque of its Mercury F2.5 portable outboard competition, which is de-rated from 3.5hp. And because the piston stroke is much longer in relation to cylinder bore diameter, vibration levels are significantly higher. On my 3.8-metre Fairlite Gull fibreglass dinghy the vibration levels were almost intolerable, whereas an F2.5 transmitted hardly any vibration. However, on my mate Richard Ardizzone’s Walker Bay 10 dinghy, which has a strong polyethylene hull, the vibration was easily absorbed.

Since this hull has a relatively short waterline length that limits hull speed, I swapped for the optional 4.5-inch pitch weedless alloy prop which enabled the engine to rev well out. Even with the small prop it pushed the Walker Bay well past hull speed and delivered very good fuel economy because the engine was never overloaded. The integral tank gave well over two hours of cruising and when throttled back to trolling rpm, up to 10 hours!

The loan engine was carefully run in on two other hulls before commencing performance and fuel-flow trials on Richard’s Walker Bay. Oil smoke appeared only after the engine had been laid on its side during transportation. It started incredibly easily, taking no more effort than the Suzuki DT2.2 outboard and using just the choke when cold as this is cross-linked with the throttle. The effective thermostat enabled the engine to warm quickly from cold.

 

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Engine condition after 10 years

For its entire life the Suzuki DF2.5 has only used Quicksilver FCW SAE 10W30 oil, which I believe to be one of the finest marine four-stroke oils available. It’s rated to handle ambient temperatures to over 40 degrees.

Over the first 48 hours of running – until the water pump impeller was replaced – it averaged 0.40L/h with 7.5 per cent of wide-open throttle operation, and the fuel/oil ratio was 630:1. But from 48 to 90.6 hours, with the same fuel consumption and WOT percentage, this improved to a very impressive 2590:1. Since then the engine has clocked up another 10 hours, so for a four-stroke it’s barely run in.

Saltwater corrosion resistance has been a little disappointing, with paint bubbling around the leg/lower unit join and rust on the driveshaft. But the second impeller is still pumping water like new and when the engine did suffer cooling loss the lower unit and thermostat were easily removed to clean out the cooling water passages. Richard used compressed air to clear deposits and since then no cooling water starvation has occurred.

 

The Trade-a-Boat verdict

Mounted on displacement hulls and inflatables to three metres that have transom heights of no more than 15 inches, the DF2.5 is a beaut little engine that’s way better value than its long-deceased two-stroke counterparts. It’s frugal, incredibly reliable and can reduce flab when needed. What more could you ask for?

For your nearest dealer, contact The Haines Group.

 

Suzuki DF2.5 portable outboard sea trials

Walker Bay 10 dinghy, total 270kg including two adults; 4.5in prop, averaged over two-way runs on Lake Macquarie NSW in calm conditions.

Throttle

RPM

SPEED (kt)

L/h

L/nm

Closed/trolling

1500

2.0

0.1

0.05

Half

4400

5.0

0.6

0.12

WOT

5400

5.6

0.9

0.16

Cruising loop (averaging 4.0kt with 10 per cent WOT) fuel flow 0.45L/h.

 

Suzuki DF2.5 outboard specs

Suzuki DF2.5 price: $1125 RRP

Engine type  Single-cylinder four-stroke petrol outboard motor

Rated BHP/MHP*    2.4/2.4 at 5500rpm

WOT RPM range      5250 to 5750

Displacement 68cc

Bore x stroke 48x38mm

Gear ratio       2.15:1

Weight           13.0kg (dry, short shaft)

OEDA stars   3

* Brake horsepower/metric horsepower or PS

 


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